Once upon a time, a sage was living in forest. He was famous for strictly following his policy of always speaking truth. One day, sage was teaching his disciples about importance of truth. He said, "We should always tell truth, no matter how difficult situation is."Suddenly a deer came running towards him. Deer bowed down and asked for help and then went inside sage's cottage quickly to hide. Moment later, a hunter also came running with his bow and arrow. Hunter knew that sage never tell lies. So, he asked him if he has been seen the deer. Sage knew hunter wants to kill the deer. At that time contrary to his nature, said, "I was busy in teaching my disciples. I haven't seen any deer here."Hunter went back to forest, thinking that deer would have gone to another direction. After hunter left, sage went inside his cottage and gave water to frightened deer and console him and calm down. Disciple who were watching this whole incident, couldn't understand the sage's act. So, one of disciple asked sage about this and requested him to clear confusion. Sage said, "My dear students, I know that you all are confused because I always ask you to follow path of truth but now I did opposite.when it comes to some innocent's life then you have to decide the correct way.I did what I thought is correct. if I would have said the truth then hunter would have killed innocent deer, which did no harm to him. so to save deer's life, I had to lie."At that moment, deer that in sage's cottage, took form of god and blessed him. 
Truth is greatest virtue. One should never tell lie but when it comes to save some innocent life then we should act accordingly. 